1. Field of Invention
The present invention relates to a machine that bends tubing. The machine employs linear ball bearings to reduce friction in the system.
2. Description of Art
Manufacturers of industrial equipment have been building tube bending machines to bend tubing for decades. One such machine is a vertical compression bending machine. A vertical compression bender makes use of a ram die and two wing dies. During the bending process, the ram die, along with a supporting ram assembly, advances in a linear fashion toward the two wing dies. A tube, supported by the two wing dies, is initially contacted by the ram die during the advancement of the ram assembly. After the ram die makes initial contact with the tube, it continues to push through the tube while forcing the wing dies to rotate away and outward from the ram die. The ram die sees resistance from the tube along with the resistance from the wing dies. In order for the tube to stay up and inside the ram die during the bending process, the wing dies must provide a counter force (cushion) in a direction against the advancing ram die. The counter force from the wing dies will hold the tube in a firm position against the ram die. The ram die continues to advance while at the same time overcoming the resistance of the tube and wing dies. The ram die continues to advance until the tube reaches the required bend angle. At that point, the ram assembly reverses direction and returns to its home position. The wing dies also reverse direction and both wing dies rotate back to their home position.
Over the years manufacturers have relied on various types of wear pads to guide the ram assembly during the bending process. A typical wear pad is constructed from bronze and acts as a bearing surface guiding the ram die and thus the ram assembly during a bending stroke. Wear pads were designed into this application decades ago because they afforded the best load bearing capability at a reasonable cost.
A compression bender is depicted in U.S. Pat. No. 2,997,141 issued to Bower et al. The Bower et al. patent shows a bender that uses guide members 25 and 26 along with wing slides 29 and 30 to ensure that the ram die 36 is guided along a linear path during a bending operation. The guide members 25 and 26 act as wear plates. These wear plates, most often constructed from a bronze material, are the bearing surfaces that allow the ram die to lynamically thrust to and from the wing dies while at the same time providing a bearing surface guide the ram assembly along a linear path.
The Bower et al. patent also uses the same approach when guiding the motion of the piston rods 87 and 96. Bower et al. relies on the bushings inside the cushion cylinders 77 and 78 to help support the forces on the piston rods 87 and 96. Cylinders 77 and 78 provide a counter force (cushion) to the advancing ram die 36. This counter force is transmitted to the ram die 36 through the wing dies 59 and 66 and the tube.
One disadvantage of the Bower et al. patent is the friction associated with the wear plates that guide the ram assembly. These bearing surfaces often require constant maintenance and eventually will need to be replaced due to the friction associated with the wear plates.
Another disadvantage of the Bower et al. patent is the side loads on the piston rods 87 and 96. These side loads will in time require unnecessary maintenance and thus the bushings in the cylinders 77 and 78 will have to be replaced. In general, these bushings should never take side loading.
Accordingly, several objects and advantages of my invention are:
(a) to reduce the friction associated with the ram assembly during a bending operation;
(b) to reduce the cost of maintenance associated the ram and cushion assemblies;
(c) to reduce the friction of the bearing assembly used to guide the cushion assembly; and
(d) to prevent a side load from imparting on the cushion cylinder""s piston rod.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
The foregoing objects and advantages can be achieved by providing a vertical compression bending machine comprising a first wind die which supports a second part of the tube, a frame supporting a first linear rail, a first linear bearing which slidably moves along the first linear rail, a ram block mounted to the first linear bearing, and a ram die, mounted to the ram block, which vertically moves to form a bend in the tube, wherein the ram block and first linear bearing move in conjunction with the ram die so that the first linear bearing slides along the first linear rail, and the first and second wing dies provide movable support to the tube as the ram die bends the tube.